meta user
network profile
| bio | website | |
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| visits | member for | 1 year, 3 months |
| seen | 19 hours ago | |
| stats | profile views | 42 |
I am a beginning math grad student studying for a written qualifier exam. All questions I ask here are taken from old exams, and none are "homework" problems, i.e. for credit (unless tagged as such).
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2d |
awarded | Popular Question |
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May 13 |
asked | Conditional Random Variable and Iterated Expectation |
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May 11 |
awarded | Popular Question |
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Feb 17 |
comment |
QuickSort Average Case Analysis: Probability of a Compare In the QuickSort algo, the probability that $z_i$ and $z_j$ is compared for $j>i$ is $2/(j-i+1)$. The reason is because if we pick an element between $z_i$ and $z_j$ to act as a pivot before we pick either $z_i$ or $z_j$, then $z_i$ and $z_j$ are fed into different recursive calls and never compared. I don't understand why we ignore $z_1$ up to $z_{i-1}$ and $z_{j+1}$ up to $z_{n}$ in the analysis, where $n$ is size of array. |
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Feb 17 |
asked | QuickSort Average Case Analysis: Probability of a Compare |
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Feb 10 |
awarded | Yearling |
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Jan 4 |
accepted | Closed form for coefficients in Multiple Regression model |
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Jan 1 |
revised |
Closed form for coefficients in Multiple Regression model deleted 1 characters in body |
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Jan 1 |
comment |
Closed form for coefficients in Multiple Regression model I've edited my post to make it somewhat clearer. If we think of the predictor variables as random variables $X_i$, I'm asking if the regression coefficients take the given forms. If we had a data matrix of observed values for the explanatory and response variables, then covariance and variance would be replaced by their estimators. |
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Jan 1 |
revised |
Closed form for coefficients in Multiple Regression model added 37 characters in body |
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Jan 1 |
comment |
Closed form for coefficients in Multiple Regression model I'm familiar with the normal equation and matrix solution. I was looking for a clean expression for $\beta_i$ that wouldn't require computing a matrix inverse. Is my conjecture for $\beta_i$ incorrect? |
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Jan 1 |
asked | Closed form for coefficients in Multiple Regression model |
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Dec 30 |
accepted | Integral of $\cos^{n}(x)$ on $[0,2\pi]$ for $n$ a positive integer |
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Dec 30 |
accepted | $\epsilon-\delta$ continuity of $1/\sqrt{x}$ |
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Dec 30 |
accepted | Norm inequality on Complex Numbers. |
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Dec 30 |
accepted | Application of Lagrange Multiplier? |
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Dec 28 |
comment |
Regressing $Y$ back on the residuals I'm still having some trouble. I understand the orthogonality property, but the equations I am finding doesn't seem correct. |
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Dec 27 |
asked | Regressing $Y$ back on the residuals |
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Dec 27 |
accepted | What is $Cov(\hat{Y},Y)$? |
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Dec 27 |
awarded | Commentator |
